(1) Field of the Invention
The present invention relates to an apparatus for adjusting the vertical position of drills in a multiple spindle drilling machine for wide flange steel beams or the like.
(2) Description of the Prior Art
When both the front and rear ends of a flange 102 of a wide flange steel beam 101 are drilled as shown in FIG. 1 according to the conventional method, upper and lower two rows of drills located on both the left and right sides of the beam 101 are similarly shifted to some extent in the front-rear direction and the portion 111 is first drilled from both the sides. Then, the beam 101 is shifted backward (in the direction indicated by an arrow 121) and the two rows of the drills are slightly shifted in a direction reverse to the above shifting direction and the portion 112 is drilled from the left and right. Then, the beam 101 is turned in the direction indicated by an arrow 122 and the portion 113 is drilled. Then, the beam 101 is shifted forward and the drills are shifted as in the case of drilling of the portion 111, and finally, the portion 114 is drilled.
According to this conventional method, shifting of the drills in the front-rear direction should be conducted three times and turning of the wide flange steel beam 101 should be conducted once. The forward and backward shifting of the drill groups is especially troublesome. This is a fatal defect involved in the conventional methods.